Let me first say straight up: the old Coak of Mists was overtuned. The combination of the extremely short cooldown and four seconds of insta-kills was too strong on the highest difficulties compared to other short cooldown offensive ults. However, I think removing the synergy between CoM and Vanish is absolutely the wrong way to balance the ult.
CoM and vanish gave something unique to shade: actual assassination gameplay. Instead of being yet another frontline melee class with a crit ult (like WHC) shade players could stealth through enemies and decimate them from behind. The tactic wasn’t without risk, as a failure to proc vanish would cause enemies to instantly turn around and slap you from all sides. No other build in Vermintide offered this style of gameplay, and many players found its uniqueness a refreshing change of pace.
As I stated above, I completely agree the old CoM + Vanish was overtuned, but it didn’t deserve to be removed from the game. Decreasing the cooldown reduction on CoM while still allowing the synergy with Vanish would have brought it in line with other kill ults without destroying its unique playstyle. Fatshark said in the patch notes they would be closely monitoring feedback, so I fervently hope they considering alternatives to balancing CoM which still allow for Shade to play like an assassin.
Thank you for continuing to keep Vermintide awesome, and for listening to your playerbase.